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RE: Steel Stair with horizontal bracing

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I have also been on long industrial stairs that seemed to sway. If I recall correctly, they all had grating treads. I would suspect that pan construction with closed risers provides a much more rigid system, similar to providing a continuous diaphragm or continuous bracing. 

Jim K.

-----Original Message-----
From: John Riley [mailto:jriley(--nospam--at)cbbel.com]
Sent: Tuesday, March 08, 2005 2:31 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Steel Stair with horizontal bracing


Bill,
I share your opinion that treads should not be considered adequate lateral
bracing for stringers.  Stair suppliers have used MC12X10.6 as stringers for
years, they work OK for short runs when the whole system is captured by
walls, but otherwise no way.  I use HSS stringers designed as unsupported.
Yeah, they can get big, but we all know size matters.
John Riley

--------------
Last week I was on a long stair to a tall building roof - I could feel
the stair sway sideways slightly as I walked up it. 

If the stringers are designed for the span as laterally unsupported,
they should be okay - but I think that stringers are often assumed to be
laterally supported due to the stair treads. (I think this was discussed
on this list a few months ago.) I think that the treads help some but I
don't think that they provide full lateral support. 

William C. Sherman, PE 
(Bill Sherman) 
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com
 

> -----Original Message-----
> From: Stuart, Matthew [mailto:mstuart(--nospam--at)schoordepalma.com] 
> Sent: Tuesday, March 08, 2005 10:18 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Steel Stair with horizontal bracing
> 
> Walk on a long  industrial stair as you described below 
> without the horizontal diagonal bracing and see what it feels like.
> 
> Matthew Stuart
> Structural Dept. - Manalapan
> 732-577-9889 x1283
> 
> 
> -----Original Message-----
> From: Aswin Rangaswamy [mailto:aswinpe(--nospam--at)hotmail.com]
> Sent: Tuesday, March 08, 2005 12:10 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Steel Stair with horizontal bracing
> 
> I have come across a stair design with bracing being provided 
> below the threads (horizontal chevron like configuration 
> bracing, spanning from stringer to stringer). This is a 
> regular self supporting one story stair with channel 
> stringers and metal pan threads.  Landing consists of 4 
> columns braced either direction.
> 
> Wanted to get your opinion as to why this is done and if it 
> is really required.  The braces were probably added to 
> transfer the in-plane forces to the stringer but the welding 
> in from the thread to the stringer should possible be 
> sufficient.  I have come across these (and similar with 
> tension rob x-bracing) in refineries and plants but not in buildings.
> 
> But are these required?
> 
> Thank you
> 
> - Aswin
> --------------------------
> Aswin Rangswamy, P.E.
> Los Angeles, California
> --------------------------
> 
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